The present invention is an improvement on the alloys described in U.S. Pat. No. 4,292,077, issued to the applicants herein and having common assignee herewith. As indicated in the patent, the new alloys are comprised of aluminum, niobium and titanium. The compositional ranges for the patented alloys were quite narrow since changes in properties were discovered to be very sensitive to the precise composition. Generally, the patented alloys contain titanium, 24-27 atomic percent aluminum and 11-16 atomic percent niobium. The alloys have at least 1.5% tensile elongation at room temperature and good elevated temperature creep strength, thus permitting their potential substitution for certain nickel base alloys such as INCO 713C.
In an important embodiment of the prior invention, vanadium partially replaces niobium in atomic amounts of 1-4%. This substitution desirably lowers the density of the alloy but at the same time the favorable high temperature properties are retained. An optimum atomic composition range for this embodiment is 24-26% aluminum, 10-12% niobium and 2-4% vanadium.
While the foregoing patented alloys meet the requirement of having creep rupture life at 650.degree. C./380 MPa which is equal to INCO 713C on a density adjusted basis, the alloys have less tensile strength at temperatures up to 400.degree. C. than does the commercial beta processed alloy Ti-6-2-4-2 (by weight percent Ti-6Al-2Sn-4Zr-2Mo). Consequently, compositional modifications of the patented alloys were evaluated to see if improvements could be achieved. As the general field of titanium alloys indicates, there are many potential alloying ingredients. But, as the prior work demonstrated, the composition of useful Ti.sub.3 Al alloys is extremely critical. Many elemental additions which have been common in other titanium alloys were previously shown to be of no advantage in Ti.sub.3 Al alloy.